In recent years, there has been an increasing interest in the use of technology to assess forces transferred to various joints, muscles, and limbs and their relative positions to each other as well as their global position at each and every moment during normal daily activities, during training loads of an exercise, or during a competitive or high intensity athletic endeavor. Efforts have been made to utilize global positioning system (GPS) devices to record running speed and estimate running performance, or to monitor human body movement and create a movement economy profile using data from measurement devices determining general body movement relative to the speed of the human body, or to estimate muscle power and joint force of limbs in order to obtain skill-related fitness parameters corresponding to the sensing of a sensing module. These known prior arts are as follows:                US 20140300490 A1, Wearable computing device for secure control of physiological sensors and medical devices, with secure storage of medical records, and bioimpedance biometric        US 20110246123 A1, Personal Status Monitoring        WO2009042390//US20120130673//U.S. Pat. No. 8,461,999 B2, Capturing body movement related to a fixed coordinate system        WO 2013063159 A2//US20130150121, Method to provide dynamic customized sports instruction responsive to motion of a mobile device        US 20120046901 A1, Motion capture apparatus        WO 2014043757 A1, Stride detection        US 20110092860 A1, System for clinical assessment of movement disorders        U.S. Pat. No. 8,821,417 B2, Method of monitoring human body movement        WO 2013072234 A1, Physical exercise correctness calculation method and system        U.S. Pat. No. 8,523,741 B2, Method and system for monitoring sport related fitness by estimating muscle power and joint force of limbs        WO 2010055352 A1//US20110218463, Assessment of gait        WO 2005002436 A1, Motion monitoring and analysis system        WO 2002018019 A1, Rehabilitation device        
In general, rate of anterior cruciate ligament (ACL) injuries per student athlete and among young people in high school and college is very high. For instance, one in every hundred college basketball players tears his or her ACL every year. So, just in Washington, D.C. metro area, in terms of the college basketball teams at George Mason, Georgetown and GW, roughly one basketball player tears their ACL every year. High school athletes also bear an extremely high risk of getting hurt. The incidence of ACL injuries is currently estimated at approximately 200,000 annually, with 100,000 ACL reconstructions performed each year.
Over 70% of ACL tears occur in a non-contact mechanism; that is, an injury happening during one body's own activity with no contact or direct involvement of others—no tackle hit, or even a touch from others. A tear occurs in a non-contact mechanism when forces generated by the body during an activity are not controlled properly, allowing excess forces to be transferred to the ACL, resulting in a tear. Balance, leg alignment, muscle strength, and muscle coordination are all extremely important factors directly affecting ACL-tear risk. The way a patient or person controls his or her body weight under motion, the way in which he or she bends or straightens the leg, and the way he or she fires or controls muscle activation for any given set of exercises or during sports all affect the ACL-tear risk. Most people with a torn ACL will experience instability, a feeling that the knee gives way or feels loose. This instability commonly results in a reduction in activities, especially sports. More importantly, the instability will usually lead to additional damage to the knee if left untreated.
One of the most common causes of non-contact ACL-tears is ACL reconstruction surgery. Patients who go through ACL reconstruction surgery bear a risk of needing a second knee surgery within two years. Studies have shown up to a 20 to 30% chance of having subsequent knee surgery after having an ACL reconstruction. There are several important parameters that affect injury or re-injury risk. For example, the alignment of the lower extremities relative to the hips is the most important and well documented; however, the degree the knee is bent for jumping and landing activities and absolute muscle strength are also important factors to consider. The variations of ideal alignment, or the degree of knee bend, or muscle strength should be calculated and tracked from the beginning of rehab to the end.
An important way to prevent non-contact injuries is to evaluate and eventually improve neuromuscular efficiency. As defined by the National Academy of Sports Medicine, neuromuscular efficiency refers to the ability of the nervous system to properly recruit the correct muscles to produce and reduce force as well as dynamically stabilize the body's structure in all three planes of motion. This is tied closely to reaction time and muscle memory. For example, neuromuscular efficiency is involved when an individual is pushed or shoved unexpectedly. How quickly the individual regains his or her balance is directly related to neuromuscular efficiency; that is, people with high neuromuscular efficiency will recover from the push very rapidly because the brain and central nervous system, generally, interact with the muscles relatively quickly, while those with low neuromuscular efficiency will take longer to recover or may even fall down. For that reason, people with a low neuromuscular efficiency tend to be more injury prone than those with a higher neuromuscular efficiency. In fact, it is believed that improving one's neuromuscular efficiency may reduce the likelihood of injury or re-injury by as much as 70 percent.